The Berkshire-based group said the work under the three-year extension will include advising on subsea and floating production infastructure for the giant Catcher field, in which Cairn Energy has a stake.
The partners hope to bring Catcher onstream in mid 2017.
Costain said it has worked with Premier Oil on a number of development projects in the North Sea during the past four years.
The company increased its exposure to the North Sea oil and gas industry by acquiring Aberdeen-based Clerk Maxwell and EPC Offshore, in 2011 and 2013 respectively. The deals involved initial outlays totalling around £13m.
A number of trade and financial buyers have acquired Scots oil services companies in recent years.
Oil services firms have capitalised on a boom in investment in new North Sea fields in areas like West of Shetland. Spending on exisiting assets has increased amid efforts by firms to ramp up production to meet strong demand.
Costain has also won a one-year extension to a three-year contract for operation and maintenance work on the Government Pipeline and Storage System, announced in 2012. The system distributes aviation fuel to UK airports.
The value of the extension was not disclosed.
Costain said it will work with the Oil and Pipelines Agency to deliver improvements to increase the safety compliance of 16 fuel storage sites.